linux-kernel - RE: [PATCH 1/2] i2c: qup: Cleared the error bits in ISR

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Date:	Wed, 11 May 2016 21:27:40 +0530
From:	"Sricharan" <sricharan@...eaurora.org>
To:	"'Abhishek Sahu'" <absahu@...eaurora.org>, <agross@...eaurora.org>
Cc:	<architt@...eaurora.org>, <linux-arm-msm@...r.kernel.org>,
	<ntelkar@...eaurora.org>, <linux-kernel@...r.kernel.org>,
	<andy.gross@...aro.org>, <linux-i2c@...r.kernel.org>,
	<dmaengine@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <wsa@...-dreams.de>
Subject: RE: [PATCH 1/2] i2c: qup: Cleared the error bits in ISR

Hi,

> 1. Current QCOM I2C driver hangs when sending data to address 0x03-0x07
> in some scenarios. The QUP controller generates invalid write in this
case,
> since these addresses are reserved for different bus formats.
> 
> 2. Also, the error handling is done by I2C QUP ISR in the case of DMA
mode.
> The state need to be RESET in case of any error for clearing the available
> data in FIFO, which otherwise leaves the BAM DMA controller in hang state.
> 
> This patch fixes the above two issues by clearing the error bits from I2C
and
> QUP status in ISR in case of I2C error, QUP error and resets the QUP state
to
> clear the FIFO data.
> 
> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
> ---
>  drivers/i2c/busses/i2c-qup.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
index
> 23eaabb..8c2f1bc 100644
> --- a/drivers/i2c/busses/i2c-qup.c
> +++ b/drivers/i2c/busses/i2c-qup.c
> @@ -213,14 +213,16 @@ static irqreturn_t qup_i2c_interrupt(int irq, void
> *dev)
>  	bus_err &= I2C_STATUS_ERROR_MASK;
>  	qup_err &= QUP_STATUS_ERROR_FLAGS;
> 
> -	if (qup_err) {
> -		/* Clear Error interrupt */
> +	/* Clear the error bits in QUP_ERROR_FLAGS */
> +	if (qup_err)
>  		writel(qup_err, qup->base + QUP_ERROR_FLAGS);
> -		goto done;
> -	}
> 
> -	if (bus_err) {
> -		/* Clear Error interrupt */
> +	/* Clear the error bits in QUP_I2C_STATUS */
> +	if (bus_err)
> +		writel(bus_err, qup->base + QUP_I2C_STATUS);
> +
> +	/* Reset the QUP State in case of error */
> +	if (qup_err || bus_err) {
>  		writel(QUP_RESET_STATE, qup->base + QUP_STATE);
>  		goto done;
>  	}
       In qup_i2c_xfer and qup_i2c_xfer_v2 state is set to RESET at the end,
when
       there is no error. So would it be fine if we do it there
unconditionally ?

Regards,
 Sricharan